Problem 42: How many triangle words does the list of common English words contain?

This problem is designed to make use of several tools.

let problem42a =
    let triangle n = let n' = n |> float in (0.5)*(n')*(n'+1.) |> int
    let tseq = Seq.initInfinite (fun i -> triangle (i+1)) |> Seq.cache
    
    let wordValue (s:string) = s |> Seq.sumBy (fun c -> (c |> int)-64)
    
    let text = System.IO.File.ReadAllText("words.txt")
    let words = text.Split([|',';'"'|], System.StringSplitOptions.RemoveEmptyEntries) |> Seq.readonly
    
    let isTriangleWord w =
        let wv = wordValue w
        tseq
        |> Seq.takeWhile (fun t -> t <= wv)
        |> Seq.exists ((=) wv)
        
    words
    |> Seq.filter isTriangleWord
    |> Seq.length